Alternating-current motor.



No. 745,325. v PATENIED DB0. 1, 190g.

- A. 1. GHURGHWARD.

ALTERNATING GURRENT MOTOR. AIEPLIOATION FILED MAR. 29, 1897. H0 MODEL. Y 2 SHEETS SHEET 1t WITNESSES: INVENTOR 6, Jiazandfir J (Zamb 5 HIS ATTORNEY no M01151 PATENTED DEC. 1, 1903.. A. J. GHURGHWARD. ALTERNATING CURRENT-MOTOR;

APPLICATION FILED MAR. 29,1897.

2 SHEETS-SHEET 2.

INVENTOR HIS ATTORNEY NITE STATES Patented December 1, 1903.

PATENT Orrrcn.

ALTERNATlNG-CURRENT MOTOR.

SPECIFICATION forming part of Letters Patent No. 745,325, dated December 1, 1903. Application filed March 29,1897. Serial No. 629,852. (ll'o modeLi T0 at whom it may concern.-

Be it known that I, ALEXANDER J. CHURCH- WARD, a citizen of the United States, and a resident of Brooklyn, in the county of Kings and State of New York, have invented a certain new and useful Alternating-Ourrent Motor, of which the following is a specification.

My invention relates to alternating-current electric motors generally, but isparticularly useful with those which by proper organization and arrangement of circuits are self starting under the influence of a single-phase alternating current.

The general object of the invention is to provide for the efficient operation and the ready control of such motors.

The invention is designed especially for use with motors which have any usual direct-current armature-winding and commutator and may be operated by feeding alternating currents to the commutator and field simultaneously, the field-coils being preferablyin series with the armature. As is well known, such machines will start from rest and will accelerate and finally reach a synchronous speed, but are not selfregulatin g and will run away under light load. Moreover, such machines as hitherto constructed and operated have been very inefficient because of the large losses necessarily present in the machine, owing to the construction adopted in order that the machine may have suflicient starting torque and which remains as a source of loss after the machine has been brought up to the normal running speed.

My invention consists, essentially, in the combination, with the machine, of a transformer supplying alternating currents thereto and suitably wound to permit its voltage to be regulated, as hereinafter described, through the medium of suitable switch devices that serve to throw in windings of the transformer to give an excess voltage at starting and afterward to throw out said windings and thereafter control the speed by preferably throwing out windings of the transformer and reducing the voltage supplied thereby when the speed rises above the normal or desired. working speed and throwing in windings and increasing the voltage when the speed falls below such normal speed. The switch devices may be worked by hand or may be controlled by speed-responsive devices which act in accord with the speed of the armature. A suitable device for the purpose is a centrifugal governor.

Then a motor having a direct-current armature and commutator is operated by a sin glephase current and run in synchronisin with the alternating-current supply, the armature becomes in effect a constant field excited by the direct current flowing in the armaturecoils. The poles of the field-magnet will alternate rapidly and will act practically as a revolving field to rotate the armature. O perated under this condition there is no appreciable loss by hysteresis in the armature or by self-induction in its wires, and if this G01ldition may be preserved the machine maybe operated with high e'l'iiciency. My present invention permits this to be accomplished by varying the windin of the transformer which supplies the current to the machine, so as to increase the voltage if the speed falls below the synchronous speed and to decrease it if the speed rises above such speed.

By the term synchronous speec I mean to include any other speed which is a multiple or submultiple of said speed, since if, for instance, the machine be run at half-speed the losses will only be due to half the reversals of the line. For example, if synchronous speed is eighteen hundred in a four-pole machine and the frequency seven thousand two hundred with half-speed the losses will only be due to three thousand six hundred alternations or at quarter-speed to eighteen hundred alternations.

In the accompanying drawings, Figures 1 and 2 illustrate my invention diagranunatically. Figs. 3, a, 5, and 0 show a form of motor and regulating mechanism by which the invention may be practiced.

In the drawings 1 have shown the invention as carried out in connection with a four-pole machine, the armature A of which is wound like any direct or continuous current generator or motor and is provided with the usual commutator,the cylinder of which is indicated at a and the brushes at b, disposed about said cylinder in the usual manner. The four-field magnet-poles are shown at c, and the field magnet coils at O. ,Ey suitable connections the field-coils are in series with the armature,

as imlieated in the diagram, or are otherwise ciimnected to the supply-oircnits, sothaindlcrnatingcurrents will llow to said coils in step with or at the same l'rcip'lency with the alternating currents ted to the commutatorbrushes and through the commutator-cylinder to the armature. I

by prel'erence l organize and operate the motorasaseriesmotorthatis,withthcarmature and lield coils in series with oneanotherand this is the condition ol. the machinebolh duringstarting or accelerat ion and when running at normal speed.

It) typilies any transl'ormer which supplies alternating currents l o the motor, as ind ica-ted in the diagrams, and which has a sectional winding permitting the voltage of said curcnts to be regulated or varied, as will be presently described.

Preferably the secondary or local it is seetionally wound tor this purpose. The primary is supplied with current lrom mains or wires l) L olf any suitable electrical condition, as well understood in the art. A switch typilied at it moves over a set of contacts numbored 11, 2, 3, l; and connected to the sections ol' coil dto permit the numln'n'otthe same to be varied in obvious manner, so as to increase or diminish the voltage el.' the alternating currents supplied to commutattw-brushes t and lield it.

-\l'hen the speed lalls l'rom the desired synchronous or other l)I'Otllfl'OllillllOtl speed, the switch is turned to increase the number of coils t/ in action, and thus increase the im pressed elcctromotive force, and when the speed rises above the predetermined or synchronous speed the switch is turned in the opposite direction to decrease the number of coils d and lower the impressed electromotive lot-re. Yfheu the machine is running at less than the full synchronous speed or in the starting operation, the alternating current liows as an alternating current in both armature and iield in series with one another, but when the synchronous speed is reached the current llows as a continucms or direct current in said armature and as an alternating current in the lield, but said lield and armature are in series, as before. by suitable adjustment of the switches the z'trmature may be kept at the synchronous speed. If desired, the machine may be kept at a lower than synchronous speed in the same manneras, for instance, at halt-speed or (piarter-spcedl1y proper znljustment ol.' the regulating devices and will then work at high cllicicncy.

The switch or etherrcgulator may be operated by hand or automatically by any device responsive to dil't'erences ol' speedas, for instance, by a centril'ugal governor typified at (i, that may be. connected with the switch or other device in any suitable way. able construction olj' J shown in Figs.

ently described.

The operation ol. the (itWtFfiS so tar as de- A suitgovernor and switch it, and t and. will be presscribed would be as follows: At starting or at low speed the switch would be on contact]. The motor would then be supplied with all of the voltage due to all the coils (1 between contact l and the opposite end of coils (7, connectcdio the lield (7. The high sell-induction ol' the motor at starting would be compensated for by the large voltage thus supplied. As the motor increases inspecd the switch would be turned, decreasing the voltage of the applied current until the synchronous speed is reached, at which time the switch rests on a contact such that the voltage would keep the motor running at that speed. On further i11- crease of speed the switch would further decrease the voltage, and the motor will drop back to the synchronous or other predetermined speed. \Vhen the motor is at rest and current turned on, there are eddy-current losses, sell-induction, and losses due to hys teresis, which all tend to reduce the useful voltage of the line by increasing the sell.'induction of the motor, so that it the motor has to have a large starting torque the self-induction will be too great to pass su ll'icientcurrent to give the necessary torque. To allow an excess of current to [low when starting the motor, I provide some auxiliary means in connection therewith for permitting or furnishing such excess current, and thereby avoid the necessity hitherto existing of using a motor which in order to get the desired starting torque has been made unnecessarily larger or has been so constructed. thatwhen running at speed it willbeinclllcient. Suchanxiliarymeansmay be extra turns in the transformer, so that it the machine is wound to run on, say, one hundred volts we can momentarily get two hundred volts. The centrifugal governor or other suitable means may be used to cut out such extra turns. These extra turns are shown connected to an auxiliary contact X either directly or through a hand-switch .5.

A suitable mechanical construction ol. cciu tril'ugal governor and a preferred construction ol controlling-switch are illustrated more in detail in Figs. 3, 7t, and (i. The governorbal ls are secured to the ends of the elbow-levers N, mounted in a bracket N, connected to the motor-shaft. The outward radial movement of the balls is resisted by a spring connecting them. The levers engage in a groove in a sleeve 0, movableaxially on theshalftand acting against a lever l, which is connected to a rod (3, carrying the switch-contzu-t, composed in this case ola pair ol'springs R H, attached to the rod and in electrical union with one another. This contact slides in the space between the series of contacli-blocks t, insulated, from one another in a suitable box or holder and a continuous plate or block t, mounted in a box at the opposite side ol the track of the contact 11 H. The sections of coil or circuits to be controlled are connected to the contacts t, and the opposite pole of the circuits to t", and the contact it .ltol' the switch thus l'ormcd will in obvious manner as it previous contact.

moves? to and fro under the actionof the governon cut the,coil-'sections into and out of circuit. A retractor-spring W acts on the switchbar Q to help reverse its movement when. the speed falls. r 1

To obviate sparking as the switch-contact rides over the series of contacts, it should under ordinary conditions. of' use momentarily bridge successive contacts that is, make contact-with a succeeding before leaving a This means a momentary short-circuiting of adjoining contacts which flintroducesa 'seriousldifiiculty when the set i 4 carries an alternatlng current.

of coils connected to the series of contacts This diiiicult'y arises from the fact that the section of coil? shortcircuited" will bear the relation to others in circuit at thetime of asecondary of an intermediate space between attached to the switch-rod. -1 rodQ or any other suitable nections thereisinterposed a lost motioiiby means of a pin-and-slot connection, as indicated, to permit the'fs'witch trans'foruier'and heavy currents will be generated in it which, if long continued,will damage the switch contacts and will give rise to .a damaging are at the instant, of break of contact. To obviate this difficulty, lprovide means for giving the switch a snap action as it passes from each contact of the series to another in both directions of adjustment. This snap action may be provided by a bar K, having a series of projections or teeth and intermediate spaces over whichrides a springactuated catch or detent in the form preferably of a friction-roller (1, carried by a spring Q. At g in the point in the conto move freely spring-actuated slips into: each I I projections on barK in obvious manner after having been under the operation of the catch or; detent as the latter forced over thesummit of one of said projec in position-on a suitable tions. Q'lhe parts are-properly arranged, so that this quick or snap action will cause the contact to snap from. each contact-point to the next.

As will be obvious, the form of bar K and detent h, as well as the form and manner of commutator, a transformer having a variable number of coils supplying said armature, as described, and supplying the field direct, means for varying the number'of coils in action, as described, so as to decrease the'voltagewhcnthe speed rises above increase and l" it when the speed falls below a predetermined speed.

2. A self-starting singlephase alternatingcurrent motor, operated at synchronous speed by alternating current fed direct to its field and toacontinuous or'directcurrent armature- Winding through the commutator therefor, in. combination with a transformer having a variable winding supplying said alternating currents, and means for automatically varyto-the speed, as and for the purpose described.

3. Asingle-phasealternatingcurrentmotor operated by alternating currents fed to the commutator of a direct or continuous current armature winding, in combination with a transform er supplying said currents, and means, such as a centrifugal governor responsive to difierences in speed of the armature for connecting and disconnecting transformercoils so as to keep the motor at a synchronous r predetermined speed.

rent motor, of a transformer supplying alternating current thereto and having a sectional windin g, a switch controlling said winding, and means for automatically operating impressed electromotive force upon the motor-- desired.

5. The combination with an alternating-current motor, of a sectional transformer supplying alternating current thereto, and means responsive to variations in the speed of the machine for varying the electromotive force supplied by said transformer to keep the speed constant.

p 6-. The combination with an alternating-current motor, of a transformer supplying said motsr and suitably wound to provide an excess of voltage for starting, and a switch for whereby after starting normal voltage may be supplied thcre by to the motor while running. at speed.

7. Thecombination with an alternating-cur, rent motor, of a transformer supplying current thereto and wound to give an extra voltage at starting, means for cutting out the extra voltage-windings after speed is attained, an automatic speed-regulator operating on the windings of aid transfhrmer to keep the speed constant, as and for the purpose described.

ing and commutator, a transformer supplying alternating currents thereto and adapted to furnish an excess voltage for starting, a sec tional winding for said. transformer, and means for cutting outih'winding by which the motor is brought up to speed, and for automatically varying the winding after speed is attained so as to keep the same constant.

, 9. The combination with a alternating-curcurrent source rent motor, of an 4. The combination with an alternatin cur said switch; from the motor so as to vary the terminals according to the torque or speed 8. The combination with a series-woundmotorhaving adirect-current armature-wiuding the number of coils in action according controlling the windings of said transformed current source in such a manner as to decrease the said electromot-ive force as the c ll -for supplying current thereto, and means op- 'the motor decreases.

& r 745,325

Sighed at NewYork, in the coun tyof New erated by the motor for'automatically vary-' York and; .State of New York, this 20th day to i'ngthe electromotive forceof said alternatingof February A. l). 1897. v

ALEXANDER J. CHURCHWARD.

Witnesses:

Wm. H. CAPEL,' D: H. DECKER...

speed of the motor increases and to increase the said electr'omotive' force as the speed of 

